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Issue 37, 2011
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An X-ray absorption spectroscopic study on mixed conductive La0.6Sr0.4Co0.8Fe0.2O3−δ cathodes. I. Electrical conductivity and electronic structure

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Abstract

The electrical conduction mechanism of mixed conductive perovskite oxides, La0.6Sr0.4Co0.8Fe0.2O3−δ, for cathode materials of solid oxide fuel cells has been investigated from electronic structural changes during oxygen vacancy formation. La0.6Sr0.4Co0.8Fe0.2O3−δ was annealed under various oxygen partial pressures p(O2)s at 1073 K and quenched. Iodometric titration indicated that the oxygen nonstoichiometry of La0.6Sr0.4Co0.8Fe0.2O3−δ depended on the annealing p(O2), with more oxygen vacancies introduced at lower than at higher p(O2)s. X-Ray absorption spectroscopic measurements were performed at the O K-, CoL-, FeL-, CoK-, and FeK-edges. The valence states of the Co and Fe ions were investigated by the X-ray absorption near edge structure (XANES) at the Co and FeLIII-edges. While the Fe average valence was almost constant, the valence of the Co ions decreased with oxygen vacancy introduction. The O K-edge XANES spectra indicated that electrons were injected into the Co 3d/O 2p hybridization state with oxygen vacancy introduction. Both absorption edges at the Co and FeK-edge XANES shifted towards lower energies with oxygen vacancy introduction. The shift at the CoK-edge resulted from the decrease in the Co average valence and that at the FeK-edge appeared to be caused by changes in the coordination environment around the Fe ions. The total conductivity of La0.6Sr0.4Co0.8Fe0.2O3−δ decreased with decreasing p(O2), due to a decreasing hole concentration.

Graphical abstract: An X-ray absorption spectroscopic study on mixed conductive La0.6Sr0.4Co0.8Fe0.2O3−δ cathodes. I. Electrical conductivity and electronic structure

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Publication details

The article was received on 30 Mar 2011, accepted on 26 Jul 2011 and first published on 17 Aug 2011


Article type: Paper
DOI: 10.1039/C1CP20982E
Phys. Chem. Chem. Phys., 2011,13, 16637-16643

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    An X-ray absorption spectroscopic study on mixed conductive La0.6Sr0.4Co0.8Fe0.2O3−δ cathodes. I. Electrical conductivity and electronic structure

    Y. Orikasa, T. Ina, T. Nakao, A. Mineshige, K. Amezawa, M. Oishi, H. Arai, Z. Ogumi and Y. Uchimoto, Phys. Chem. Chem. Phys., 2011, 13, 16637
    DOI: 10.1039/C1CP20982E

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